Hardening of gelatin



United States Patent 'HARDENING OF GELATIN Charles F. H. Allen and Thomas T. M. Laalrso, Rochester,

N. Y., assignors to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey No Drawing. Application December 1, 1951, Serial No. 259,511

. 14 Claims. (Cl. 106-125) This invention relates to the hardening of gelatin either when applied as an emulsion layer on a support, such as film, plate or paper, or when applied in the form of a solution as a simple coating or sizing for paper'or the like.

In the preparation of photographic emulsions it has been the practice for many years to overcome the tendency of the gelatin to melt orto swell during development, particularly during high temperatures, by the addition of various so-called hardening agents, some of which are chrome alum, formaldehyde, acrolein, glyoxal, saturated diketones and the like.

We have discovered a new class of hardening agents for photographic gelatin, namely bis-esters of methane sulfonic acid of the general formula where x is either a straight bond, c.H. '0-ctH.

or 1, 2, 3 or 4 CH2 groups. We have found the compounds characterized by this formula to be eminently suitable for the purpose of hardening gelatin. By incorporating small amounts of a compound of this type in gelatin compositions we have found that gelatin emulsion layers or gelatin layers in general are capable of resisting ject of our invention is to provide a process of hardening gelatin coatings or layers generally whether in the form of a photographic emulsion or merely in the form of a layer or coating on paper or some other support therefor. Other objects of our invention will appear herein.

In the present invention the above objects may be ac complished by incorporating into an aqueous solution of gelatin or into a gelatin photographic emulsion a small proportion of a bis-ester of methane sulfonic acid. After the composition, which also forms a part of our invention, has been coated out onto a support, it is then subjected either to an elevated temperature or to long standing, which treatment increases the hardening efiect. We have found that any amount of one of these compounds has a hardening effect upon the gelatin, but it is usually 'desirable that at least 0.025 part of the hardenerper 15.5 parts of gelatin be present to give an effective hardening, it being preferable to use approximately 0.25 part of the hardener per..15.5 parts of gelatin. The hardener can be employed in proportions up to as much as M by weight of the gelatin, but as the preferred proportion given is ice Example 1.-1,2-di-(methanesulfonoxy)-etharie 310 parts of dry ethylene glycol was dissolved in 1500 7 parts of dry pyridine, and 1150 parts of methanesulfonyl chloride was slowly added to this solution with vigorous stirring. The temperature of the system was maintained between 5 and 15 C. After the reaction was completed the mass was stirred into three times its volume of finely crushed ice. The crystalline product which separated was I washed with ice water and then dried. The product was obtained in the form of white crystals having a melting point of 45-47 C. and a yield of 77% of theoretical.

Example 2.--1,3-di-(methanesulfonoxy)-pr0pane 152 parts of trimethylene glycol was dissolved in 600 parts of dry pyridine, and 460 parts of methanesulfonyl chloride was slowly added thereto while vigorously agitating and maintaining the temperature between 5 and 15 C. After the reaction was completed the mass was stirred into three times its volume of. finely crushed ice. The crystals obtained were washed with ice water and dried. These crystals were recrystallized from ethyl alcohol.

The crystals obtained had a melting point of 41942 C.

Example 3.-1,5-di-(methanesulfonoxy)-pentane ride was added to this solution with vigorous stirring while the temperature was maintained between 5 and 15 C. After the reaction was completed, the mass was stirred into three times its volume of finely crushed ice. The crystalline product which separated was washed with ice water and dried. White crystals were obtained having a melting point of 3536 C.

Example 4.fl,p-di-(methanesulfonoxy)-diethyl ether 212 parts of dry diethylene glycol was dissolved in 1200 parts of dry pyridine, and 460 parts of methanesulfonyl chloride was slowly added to the solution with vigorous agitating while maintaining the temperature between 5 and 15 C. After completion of the reaction the mass was stirred into three times its volume of finely crushed ice and the crystalline product was purified as in the preceding examples. White crystals were obtained having a melting point of 57-58" C.

The various compounds prepared as above were used for hardening gelatin by adding to 200 cc. portions of a photographic emulsion containing approximately 15 /2 grams of gelatin, 0.025 gram and 0.25 gram respectively of p the compound in solution in methanol. Also, a control coating was made with the same batch of emulsion, but 1 without hardener. After coating the emulsion upon a support therefor, the coated support was incubated one day at F. and 50% R. H. to complete the hardening process. The degree of hardening was then determined by immersing the coatings in water at 70 F. and gradually raising the temperature to the point at which the coating disappeared from the support, the rate of increase in temperature being the same in all tests, and the water being stirred during the process. Whereas it was found that the control coatings disappeared from the support (melted) within the range of -122 F., it was found that when using 0.25 gram of the hardener, although the temperature reached the boiling point of the water, the coating still remained thereon. When 0.025 gram of the hardener was employed, the coatings were not re- 3 moved from the support until the points indicated below were reached:

F. 1,2-di-(methanesulfonoxy)-ethane 131 1,3-di-(methanesulfonoxy)-propane 211 1,5-di-(methanesulfonoxy)-pentane 145 fl,fl'-di-(methanesulfonoxy)-diethyl ether 180 Example 5.-1,6-di-(methanesulfanoxy)-hexane 50 parts of hexamethylene' glycol was dissolved in 180 parts of 'dry pyridine, and 98 parts of mcthanesulfonyl chloride was slowly added to this solution while vigorously stirring and maintaining the temperature between 5 and 15' C. After the reaction was completed, the reaction mixture was stirred into 3 times its volume of crushed ice. The crystalline product obtained was washed with ice water and dried. It was purified by recrystallization from ethyl alcohol. The product obtained had a melting point of 57-58 C.

The above-prepared 1,6-di-(methanesulfonoxy)-hexane was employed as a hardener in photographic emulsions in the following manner: To 200 cc. portions of a silver halide-gelatin photographic emulsion containing about 8% gelatin was added methyl alcohol solutions of 1,6-di- (methanesulfonoxy)-hexane containing respectively 0.1, 0.2 and 0.4 gram thereof. The emulsions so prepared were coated onto glass plates, dried and were then conditioned by treating at 72 F. and 50% relative humidity, followed by heat sealing in foil bags and heating for 24 hours at 100 F. The melting points of these emulsion coatings were then determined in a water bath by bringing the temperature to 212 F. and holding for a maximum of 20 minutes, unless, of course, melting occurs sooner. The melting points of the coatings were as follows, a coating containing no hardener being included as a check:

1,6-di-(methane- The speed and contrast of the coatings containing the 1,6-di-(methanesulfonoxy)-hexane were satisfactory, it being found that the presence of this material had no adverse effect upon the properties of the emulsion.

We have found that instead of the incubation treatment the gelatin coating may be allowed to stand for some time at ordinary temperature, whereupon it becomes resistant to the effects of boiling water. For instance, 0.05 gram of 1,5-di-(methanesulfonoxy)-pentane was added to 200 cc. of emulsion as described above, and was coated out on a support, and the emulsion layer was kept for at least 14 days at 70 F., whereupon the resulting layer was found to resist the melting effect of boiling water.

The rate at which the hardening is effected is influenced by the temperature and the relative humidity. Therefore, if the coatings are allowed to stand under normal conditions, the time for curing is longer than when an elevated temperature is used. Also, if the curing is carried out at an elevated temperature, a decrease in relative humidity will necessitate either a higher temperature or a longer time than for a given relative humidity to obtain the equivalent degree of hardening. For instance, it has been found that maintaining at 100 F. and 50% R. H. for -1 day will give the maximum degree of hardening in accordance with our invention. However, if the relative humidity is lower, a higher temperature will be necessary to give the same effect in the given time and vice versa. The use of the combination of temperature, relative humidity and time which will give the ultimate degree of hardening in accordance with the proportion of hardener used will be referred to herein as curing. I

As indicated, our invention is applicable not only to the manufacture of photographic emulsions of satisfactory hardening properties, but may likewise be applied to the manufacture of gelatin solutions which are to be used for producing coatings on paper, cloth, film or other surfaces. Also, if desired, these hardening agents may be used in conjunction with other hardening agents, for example, aldehydes or alum.

We claim:

1. A composition comprising an aqueous solution of gelatin containing therein at least 0.025 part, per 15% parts of gelatin, of a hardening agent having the following formula:

-SOsCHI wherein X is selected from the group of (CH:)o-4 and C2Hi-O-CzH4-.

2. A composition comprising an aqueous solution of gelatin containing therein approximately 0.25 part, per 15% parts of gelatin, of a hardening agent having the formula l-BChCHs wherein X is selected from the group of (CH:)o-4 and CaH4O-CaH4-.

3. A composition comprising an aqueous solution of gelatin containing therein at least 0.025 part, per 15% parts of gelatin, of 1,2-di-(methanesulfonoxy)-ethane.

4. A composition comprising an aqueous solution of gelatin containing therein at least 0.025 part, per 15% parts of gelatin, of 1,3-di-(methanesulfonoxy)-propane.

5. A composition comprising an aqueous solution of gelatin containing therein at least 0.025 part, per 15% parts of gelatin, of 1,5-di-(methanesulfonoxy)-pentane.

6. A composition comprising an aqueous solution of gelatin containing therein at least 0.025 part, per 15% parts of gelatin, of p,p-di-(methanesulfonoxy)-diethyl ether.

7. A photographic product comprising a gelatin layer upon a support therefor, which gelatin layer contains therein at least 0.025 part, per 15% parts of gelatin, of a hardener having the formula in which X is selected from the group (CH:)e-4 and C2H40C2H4.

8. A photographic product comprising a gelatin layer upon a support therefor, which gelatin layer contains therein approximately 0.25 part, per 15% parts of gelatin, of a hardener having the formula x -SO1CH3 in which X is selected from the group (CHa)o-4 and -C2H4O-C2H4.

9. A photographic product comprising a gelatin layer upon a support therefor, which gelatin layer contains therein at least 0.025 part of 1,2-di-(methancsulfonoxy)- ethane per 15% parts of gelatin.

10. A photographic product comprising a gelatin layer upon a support therefor, which gelatin layer contains therein at least 0.025 part of 1,3-di-(methanesulfonoxy)- propane per 15% parts of gelatin.

11. A photographic product comprising a gelatin layer upon a support therefor, which gelatin layer contains therein at least 0.025 part of l,S-di-(methanesulfonoxy)- pentane per 15 /2 parts of gelatin.

12. A photographic product comprising a gelatin layer (E-SOxCH:

in which X is selected from the group (CHz)o-4 and CzH4-O--C2H4.

14. In a method of hardening gelatin, the step which comprises adding to an aqueous gelatin solution, prior to coating out upon a surface, approximately 0.25 part, per 15 parts of gelatin, of a hardener having the formula (f-BOaCH;

Werntz June 21, 1938 Simmons et al Apr. 29, 1941 

1. A COMPOSITION COMPRISING AN AQUEOUS SOLUTION OF GELATIN CONTAINING THEREIN AT LEAST 0.025 PART, PER 15 1/2 PARTS OF GELATIN, OF A HARDENING AGENT HAVING THE FOLLOWING FORMULA: 